Grapple with locking mechanism

ABSTRACT

A GRAPPLE FOR GRIPPING A SUCCESSION OF ARTICLES TO BE LIFTED IN WHICH JAWS ATTACHED TO ARMS MOVE BETWEEN OPEN POSITIONS AND CLOSED FOR GRIPPING POSITIONS IN RESPONSE TO THE ARMS BEING LOWERED TO SPREAD POSITIONS AND RAISED TO COLLAPSED POSITIONS. MOUNTED ON THE GRAPPLE IS A LATCH WHICH SWINGS BETWEEN LATCHED AND UNLATCHED POSITIONS AUTOMATICALLY IN RESPONSE TO RAISING AND LOWERING OF THE GRAPPLE THEREBY TO AUTOMATICALLY LOCK THE JAWS OPEN TO GRIP AN ARTICLE AND THEN TO AUTOMATICALLY UNLOCK THE JAWS TO FREE THE LATTER FOR MOVEMENT TO THEIR GRIPPING POSITIONS. THE LATCH IS MOUNTED BY A PIN-SLOT CONNECTION ON ONE MOVING PART OF THE GRAPPLE AND CAN HOOK AROUND A CATCH ON ANOTHER PART OF THE GRAPPLE TO LOCK THE GRAPPLE OPEN. THE LATCH IS SPRING BIASED TO SWING ABOUT THE PIN, AND THE LATTER MOVES UP AND DOWN IN THE SLOT DURING USE OF THE GRAPPLE TO CAUSE THE LATCH TO BE BIASED FIRST TOWARD THE LATCHED POSITION AND THEN TOWARD THE UNLATCHED POSITION.

Feb. 9, 1971 'P. H. DIXON GRAPPLE WITH LOCKING MECHANISM Filed Jan. 29. 1969 3 Sheets-Sheet 1 1 3 N M}; 6 m w 3 K3 333% w o a a 3 g ggg w 9g) 1 Q m \l Q B a a 2Q N a s; d

J x F T a Di KO 'L Feb.9, 1971 .XON 3,561,812

GRAPPLE WITH LOCKING MECHANISM Filed Jan. 29. 19 69 3 Sheets-Sheet 2 MVSAJTCDKJ Paul Q4. 33 L xom 'fi/J 'ML raw M Feb. 9, 1971 R HjmxoN 3,561312 GRAPPLE WITH LOCKING MECHANISM Filed Jan. 29. 1969 3 Sheets-Sheet 3 Paul -(.Dixon a dfiW-YJ; awk) United States Patent O 3,561,812 GRAPPLE WITH LOCKING MECHANISM Paul H. Dixon, Belvidere, Ill., assignor to Dixon Automatic Tool, Inc., Rockford, Ill., a corporation of Illinois Filed Jan. 29, 1969, Ser. No. 794,868 Int. Cl. B66c 1/00 U.S. Cl. 294-110 3 Claims ABSTRACT OF THE DISCLOSURE A grapple for gripping a succession of articles to be lifted in which jaws attached to arms move between open positions and closed or gripping positions in response to the arms being lowered to spread positions and raised to collapsed positions. Mounted on the grapple is a latch which swings between latched and unlatched positions automatically in response to raising andlowering of the grapple thereby to automatically lock the jaws open to grip an article and then to automatically unlock the jaws to free the latter for movement to their gripping positions. The latch is mounted by a pin-and-slot connection on one moving part of the grapple and can hook around a catch on another part of the grapple to lock the grapple open. The latch is spring biased to swing about the pin, and the latter moves up and down in the slot during use of the grapple to cause the latch to be biased first toward the latched position and then toward the unlatched position.

BACKGROUND OF THE INVENTION The invention relates to grapples for grasping and lift ing various articles and, more particularly, to a grapple with a support positionable over an article and connected to a lifting mechanism so as to be lifted and lowered through up and down strokes in response to raising and lowering of the lifting mechanism. The grapple includes a pair of crossed arms connected to the support for scissoring movement relative to one another in generally vertical planes between collapsed and spread positions. The arms scissor toward the spread positions as an incident to terminal movement of the grapple through its downward stroke and scissor toward the collapsed positions as an incident to initial movement of the grapple through its upward stroke. On the lower ends of the arms are opposed article-engaging jaws which move toward and away from one another between the gripping and open positions to grasp and release the article in response to scissoring of the arms between the collapsed and spread positions.

SUMMARY OF THE INVENTION The primary aim of the present invention is to provide a novel and simplified grapple of the above character which automatically locks in an open position after releasing one article so as to be ready to grip a second article, and then automatically unlocks to close upon and grip the second article so that the grapple can raise and lower a succession of like articles without need of manually opening the jaws.

A more detailed object is to achieve the foregoing with a unique and extremely simple latching mechanism carried on the grapple and movable automatically between latched and unlatched positions to lock the grapple open and then to free the grapple for closing. More specifically, the latching mechanism comprises a latching member connected to one part of the grapple by a pin-andslot connection and biased to swing between the latch and unlatched positions. As the grapple moves through its raising and lowering cycle, the pin is moved up and down relative to the slot causing the latching member to be biased first in one direction and then in the other to effect the latching and unlatching movement.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevation of a new and improved grapple embodying the novel features of the present invention, the grapple being shown lifting a relatively narrow article.

FIG. 2 is a view similar to FIG. 1 but showing the grapple lifting a relatively wide article.

FIG. 3 is a cross-section on a reduced scale taken substantially along the line 33 of FIG. 6.

FIG. 4 is an enlarged fragmentary view of the latching mechanism just prior to locking.

FIG. 5 is a view simililar to FIG. 4 but showing the latching mechanism after locking.

FIG. 6 is an enlarged end view of the improved grapple shown in FIG. 1.

FIG. 7 is a perspective view of the latching member shown in FIGS. 4 and 5.

FIG. 8 is a view similar to FIG. 4 but showing the latching member out of proper position and being guided into proper position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the drawings for purposes of illustration, the invention is incorporated in a grapple 10 detachably connected to a hook 11 of a lifting mechanism such as a hoist (not shown) and used to grip articles for movement of the articles by the hoist. Usually, this movement includes lifting, transporting and lowering the grapple and the article.

In this instance, the main support for the grapple 10 a is formed by two opposed support plates 12 and 13 (FIG. 6). Two vertically inclined and crossed arms 14 and 15 (FIG. 3) are mounted between the support plates and are pivotally connected to the support plates by pins 16 for scissoring movement relatively to one another. Pivotally connected at the upper end of the arm 14 (FIG. 3) by a pin 18 is a first link 19, and pivotally connected at the upper end of the arm 15 by a pin 20 is a second link 21. -A pin 22 pivotally connects the upper ends of the links, and a support or bail 23 for receiving the hook 11 is also pivoted on the pin '22. When the bail 23 is initially pulled upwardly by the hook and the hoist, the links 19 and 21 swing toward one another to lift the upper ends of the arms 14 and 15 and to swing the arms toward collapsed positions (FIG. 1). In the same manner, lowering of the hook lowers the arms and allows the arms, during their terminal downward movement, to swing toward spread positions (FIG. 3). Connected to the lower ends of the arms in opposite face-to-face relation are jaws 24 which move between open and gripping positions in response to scissoring of the arms between their spread and collapsed positions.

In this instance, each jaw 24 includes an elongated U- shaped support member 25 (FIGS. 3 and 6) with flanges 26 extending outwardly in a horizontal direction (FIG. 6) at both sides of the bottom of the U. Near the sideend (FIG. 3) of each support member 25, the lower end of the respective one of the arms 14 and 15 is pivotally connected (FIG. 6) between the upstanding legs 27 and 28 of the U-shaped support member by a pin 29 (FIG. 3). To the inside end portion of each U-shaped support member, a bell crank 30 (FIG. 3) is pivotally attached by a pin 32, and each bell crank is pivotally attached to the support plates 12 and 13 by a pin 33. Thus, the four pivot pins 16, 29, 32 and 33 form the corners of a shiftable parallelogram for movement of the jaws between open and gripping positions.

Forming the gripping surface of each jaw 24 is a downwardly extending gripping plate 34 (FIG. 3) mounted on the U-shaped support member 25. So that the grapple can be used to grip articles of different sizes including a relatively narrow article 34a (FIG. 1) or a relatively wide article 34b (FIG. 2), the upper end (FIG. 6) of each gripping plate is telescoped slidably over and is adjustable along the outwardly extending flanges 26 of the U-shaped support member 25. To look each gripping plate 24 in a given position for handling articles in a given size range, the bottom of the U-shaped member 25 is formed with teeth 35 (FIGS. 1 to 3), and a toothed locking pin 36 is slid through a hole in the gripping plate so that the teeth mate to lock the gripping plate against sliding on the flanges 26. To adjust the position of the gripping plate, the locking pin is pulled out by pulling on a ring 37 looped through one end of the locking pin so as to free the plate to slide along the flanges 26 until the desired new position is reached. The locking pin then is slid back into its hole to lock the gripping plate in the new position. To give even a wider range of adjustment, each gripping plate is formed with its lower end 38 offset in a horizontal direction from its upper end and, as shown in FIG. 1, the lower end extends inwardly for gripping the narrower articles 34a. To accommodate the wider articles 34b, each gripping plate is slid off the U-shaped support member 25, is turned end-for-end so that the offset lower end 38 extends outwardly (FIG. 2), and then is slid back onto the U-shaped support and locked in place.

It is apparent from the above that as the arms 14 and swing toward their collapsed positions, the jaws 24 are moved toward one another toward a closed or gripping position and, as the arms swing toward their spread positions, the jaws are moved away from one another to an open or release position. For purposes of keeping the jaws centered on the articles, the bell cranks 30 are connected together by a pin-and-slot connection at their ends remote from the jaws. Herein, a pin 39 (FIG. 3) fast on one bell crank rides in a mating slot 40 cut in the other bell crank.

To move an article, a four stage operation of the grapple 10 is required. First, the grapple is lowered over the article to be moved until downward movement of the support plates 12 and 13 is stopped. Such stopping where the article being handled is relatively narrow and when the jaws are turned as shown in FIG. 1 is caused by the support plates coming into contact with the article 34a. When the article is relatively wide and the jaws are turned as shown in FIG. 2, stopping of the support plates is brought about by the jaws 24 contacting an article 34b and being halted in their downward progress. This action stops the U-shaped supports which, acting through the bell cranks 30, halt the support plates in their downward movement. After the support plates stop their downward movement and with further or terminal lowering of the bail 23, the links 19 and 21 continue to lower and swing are arms 14 and 15 about the pins 16 toward their spread positions thereby moving the jaws 24 further apart or open.

In the second part of the operation, the grapple 10 is lifted to grip and raise the article. During initial upward movement of the grapple as the bail 23 is raised, the links 19 and 21 move upwardly relative to the support plates 12 and 13 to swing the arms 14 and 15 toward their collapsed positions and to move the jaws 24 toward their gripping positions until the jaws close on and grip the article. Until the jaws close on the article, the support plates 12 and 13 are not raised because all the upward motion of the bail is spent in moving the links and swinging the arms. After the jaws close on the article, the arms are prevented from swinging further toward their collapsed positions because the movement of the lower end of each arm is halted by engagement of its respective jaw with the article. Accordingly, further lifting of the grapple 10 raises the article with the various parts of the grapple moving upwardly in unison with one another.

After the article has been moved to a point over its desired location, the grapple 10 and the gripped article are lowered toward floor or other supporting surface (not shown). After coming into contact with the supporting surface, the article stops further downward movement of the support plates. Thereafter, as the hook 11 and the bail 23 continue to lower, the links 19 and 21 move downwardly to swing the arms 14 and 15 toward their spread positions and thereby move the jaws 24 to their open positions to release the article.

Finally, the empty grapple 10 is lifted off the article. During the initial upward movement, the links are raised upwardly relative to the support plates 12 and 13 thereby swinging the arms toward their collapsed positions to move the jaws toward their closed positions. Once the jaws have moved as far as they can toward their closed positions, no further relative motion between the various parts takes place. Any further lifting of the grapple 10 thus results in the empty grapple being lifted from the article.

In accordance with the present invention, the jaws 24 of the grapple 10 are automatically locked open every other time the arms 14 and 15 move an initial amount from their spread positions toward their collapsed positions, and the jaws 24 are automatically unlocked when the arms next move toward their spread positions thereby to enable the lifting of successive articles without need of manually opening the jaws each time the grapple is lowered over an article. For these purposes, a latching mechanism 41 (FIG. 3) automatically locks the jaws in their open positions and then unlocks the jaws, such locking and unlocking occurring once in response to each I four stage movement of the grapple 10. With this arrangement, the grapple can lift an article, move it, set it down, release it, and have the jaws automatically locked open so that the empty grapple may be moved and placed over a second article without the necessity of manually opening the jaws upon arrival of the grapple at the second article. After being placed over the second article, the jaws are automatically unlocked to allow them to be moved into gripping engagement with the second article.

In this instance, the latching mechanism 41 is made up of a movable latch 42 (FIG. 4) mounted on the link 21 and a catch 43 (FIG. 4) mounted on the support plate 13. The latch swings between a latched position (FIG. 5) in which the link 21 is locked to the catch and the support plate 13 to lock the jaws open and an unlatched position (FIG. 1) in which the link and the support plate are free to move relative to one another to enable closing of the jaws. When the link is locked to the support plate, upward movement of the link relative to the support plate is prevented. Without upward relative movement occurring between the link and the support plate, the arms 14 and 15 cannot swing further toward their collapsed positions and thus the jaws 24 are locked in open positions. Because, in the unlatched position of the latch, the link can move relative to the support plate, the arms are free to swing toward their collapsed positions during the initial lifting of the grapple 10, and the jaws 24 are free to move to their closed positions to grip the article.

As best shown in FIG. 4, the latch 42 of the latching mechanism 41 is mounted on a plate 44. Formed in the plate near one end is a vertical slot 45, and mounted on the other end portion of the plate is a spring housing 46. One end portion of a second plate 47 (FIGS. 1, 2 and 6) is mounted on the spring housing as a cover plate, and the other end portion is formed with a vertical slot 48 (FIGS. 1 and 2) alined with the slot 45 in the plate 44. The latch 42 (FIG. 7) is formed with a hook 50 at its lower end, and a pin 51 is rigid with the upper end portion of the latch. The pin 51 rides in the slots 45 and 48 to mount the latch on the link 21 for both swinging movement of the latch about the axis of the pin as the latter turns in the slots, and for bodily shifting of the latch as the pin slides up and down in the slots.

Mounted on the support plate 13, the catch 43 is in the form of a round stud extending from the inner face of the support plate 13. The latch 42 can be biased to swing clockwise (FIG. 4) about the axis of the pin 51 so that, at the proper time, the latch will come into contact with the catch 43. When this occurs, the hook 50 can engage the catch (FIG. to lock the link 21 to the support plate and thus lock the jaws 24 in their open positions. At the proper times, the latch will be biased counterclockwise (FIGS. 1 and 5) so that, when the hook becomes disengaged from the catch, the latch will be swung away from the catch, and the link will be free to move relative to the support plate to allow the jaws to close.

To bias the latch 42, a spring-pressed plunger 53 mounted in the spring housing 46 (FIG. 4) at a level midway between the ends of the slots 45 and 48 pushes against the latch. So that the latch may be biased first in one direction and then the other, the latch is moved at the appropriate times into a pre-lock position (FIG. 3) or a prerelease position (FIG. 5). In the pre-lock position, the latch 42 has been bodily moved upwardly to the point where the pin 51 rides at the top of the slots. By virtue of its location midway between the ends of the slots, the spring-pressed plunger 53 biases the latch 42 in a clockwise direction about the pin when the latch is in its prelock position so that, when the latch is released from the pre-lock position, the latter will swing over to the catch 43 for engagement with the catch to lock the jaws 24 open. In the pre-release position of the latch, the hook 50 engages the catch 43 and the pin 51 rides at the bottom of the slots 45 and 48 (see FIG. 5). With the pin at the bottom of the slots, the spring-pressed plunger 53 biases the latch in a counterclockwise direction (FIG. 5) so that, when the hook is disengaged from the catch, the latch will swing away from the catch unlocking the link 21 from the support plate 13 and thus releasing the jaws 24 for movement toward closed positions. As the latch moves from the pre-lock to the pre-release position, the pin 51 must move from the top of the slots to the bottom of the slots. This bodily movement of the pin in the slots gives, in effect, an over-center action of the spring-pressed plunger with respect to the pin so that the plunger first acts below the pin for clockwise biasing of the latch and then acts above the pin for counterclockwise biasing of the latch. The movement of the latch 42 from the prerelease and pre-lock positions occurs once during each four stage cycle of operation of the grapple so that the jaws 24, which are locked open when the cycle begins,

are released to grip an article and then are again locked open after the article is released.

At the beginning of each four stage cycle of operation, the latch 42 is in the pre-release position with the hook 50 engaging the catch 43 and with the pins 51 at the bottom of the slots 45 and 48 as shown in FIG. 5. In this position, the latch 42 locks the link 21 at a fixed distance from the support plate 13, and no movement of the link away from the support plate can occur thus resulting in the jaws 24 being locked in open positions. First, the empty grapple 10 with its jaws locked open is lowered over an article to be lifted until downward movement of the support plates 12 and 13 is halted by the article. With continued downward movement of the bail 23, the links 19 and 21 move downward toward the support plates, the arms 14 and 15 swing toward the spread positions, and the jaws 24 open a small further amount. As the link 21 moves closer to the stopped support plate 13, the latch 42 moves downward with the link, and the hook 50 moves out of engagement with the catch 43. When the hook clears the catch, the latch is swung counterclockwise from its pre-release position by the spring-pressed plunger 53 until the latch strikes a guide stop 54 (FIG. 4), in the form of a stud extending from the inner face of the support plate 13.

During the second part of the cycle of operation, the grapple 10 is raised and, as the bail 23 is lifted, the initial upward movement occurs. That is, while the support plates 12 and 13 remain stationary, the links 19 and 21 move upwardly to swing the arms 14 and 15 toward the collapsed positions and to move the jaws 24 into gripping engagement with the article. Since the latch 42 is being biased counterclockwise, it does not engage the catch 43 on the support plate 13 as the link 21 moves upwardly. After the jaws engage the article, further lifting of the bail 23 lifts the entire grapple 10 in unison along the article gripped between the jaws. While the grapple is being lifted, moved and initially lowered, the latch 42 is biased counterclockwise and held in its unlatched position (FIG. 1), and the pin 51 rides in the bottom of the slots and 48.

Next, the grapple 10 and the gripped article are lowered until the article contacts the support surface to stop downward movement of the article and the support plates 12 and 13. With the support plates stationary, further lowering of the bail 23 allows the links 19 and 21 to move downwardly relative to the support plates to swing the arms 14 and 15 toward the spread positions and move the jaws 24 to open positions thereby releasing the article.

As the link 21 moves downwardly relative to the support plate 13, the latch 42, still being biased in a counterclockwise direction, moves downwardly toward the support plate until the end 55 (FIG. 3) of the latch comes into contact with a stop 56 in the form of a stud extending from the inner face of the support plate 13. During this part of the terminal downward movement, the stop 54 acts to guide the latch into contact with the stop 56. The bottom end portion of the latch is formed with slanting sides 57 and 58 (FIG. 4) so that the slanting side 58 will cam off the guide stop 54 and aim the latch toward the stop 56. After the end 55 of the latch 42 contacts the stop 56, further downward movement of the link causes the slots 45 and 48 to move downwardly relative to the pin 51 until the pin abuts the top of the slots. Once the pin abuts the top of the slots and the end of the latch is against the stop 56 (see FIG. 3), the latch acts as a brace and no further downward movement of the link 21 relative to the support plate 13 can occur. As the pin changed position from the bottom of the slots to the top of the slots, the point of action of the spring-pressed plunger 53 changed from above the pin to below the pin thus changing the bias on the latch to a clockwise direction, and placing the latch in its pre-lock position (FIG. 3).

Finally, the empty grapple 10 is lifted off the article so that it can be moved to a second article to be lifted. During the initial upward movement, the links 19 and 21 move upwardly away from the support plates 12 and 13, and the arms 14 and 15 swing toward the collapsed positions to move the jaws 24 toward their closed positions. As the link 21 moves upwardly, the pressure forcing the latch 42 against the stop 56 is relieved, and the spring pressure plunger 53 forces the latch to swing the pin 51 in a clockwise direction until the face of the latch contacts the catch 43 (FIG. 4). Further upward movement of the link raises the latch until the hook of the latch engages the catch 43. If the hook should happen to slip past the catch, a second guide stop 59 in the form of a square stud extends from the inner face of the support plate 13 above and to the left of the catch 43 (FIG. 8) to act as a guide for returning the latch to its proper position. To return the latch to its proper position, the upward movement must be stopped and the latch lowered. As the latch is lowered, the guide 59 will cam the latch counterclockwise back past the catch until the latch is in proper position again.

When the hook 50 properly engages the catch 43, continued upward movement of the link 21 moves the slots 45 and 48 upward relative to the pin 51 until the pin rests against the bottom of the slots. As shown in FIG. 5, the relative movement of the pin to the bottom of the slots moves the latch 42 to its pre-release position and causes the spring-pressed plunger 53 to act above the pin and bias the latch in a counterclockwise direction toward its unlatched position. After the pin rests against the bottom of the slots, the latch locks the link at a fixed distance from the support plate 13 and, at this point, upward relative movement of the plates, links, arms, and jaws ends. Since the link 21 and the support plate 13 are locked to one another a relatively short distance apart, the jaws 24 move only slightly from their most open positions before the relative motion stops and the jaws are locked open. Thus, the empty grapple with the jaws locked open and with the latch 42 in the pre-release position can be moved from the article to a second article to be lifted at which point the cycle of operation begins again.

It is apparent that the latching mechanism 41 provides a very simple device for locking and unlocking the grapple 10 once for every four cycle operation required to move an article. Through the movement of the latch 42 into the pre-lock and pre-release positions in response to the movement of the grapple through its cycle of operation, the latch is assured of locking the jaws 24 in open positions only once and releasing them from the locked open positions at the proper point in each four stage cycle. In this way, the simple and positive acting latch insures that, when the grapple with its jaws locked open is placed on an article to be moved, the jaws will be released to grip the article. Likewise, the latch insures that, after the ar ticle has been gripped, moved, set down, and released, the jaws will be locked open so that the grapple can be used to lift a second article without the necessity of manually opening the jaws before lowering over the second article.

I claim as my invention:

1. A grapple for gripping an article to be lifted and comprising a pair of opposed jaws movable toward and away from one another between gripping and open positions, a support, a pair of vertically inclined crossed arms each pivoted intermediate its ends to the support whereby said arms may swing between spread and collapsed positions, each of said arms being connected at its lower end to a respective one of said jaws, a pair of links pivotally connected together at their upper ends and each pivotally connected at its lower end to the upper end of a respective one of said arms, said links adapted to be attached to a lifting mechanism whereby initial raising of said links swings said arms toward the collapsed positions thus moving said jaws toward one another until the latter grip an article and then further raising of the links lifts said grapple and the gripped article, initial lowering of said links being effective to lower the gripped article into contact with a supporting surface and further lowering being effective to swing said arms toward said spread positions thus moving said jaws to the open positions to release the gripped article, the improvement in said grapple comprising, means on said grapple for automatically locking said arms in said spread positions thereby locking the jaws in said open positions as the grapple is lifted after releasing the gripped article and for automatically unlocking said arms as said grapple is subsequently lowered onto another article to be gripped so that said grapple may grip an article, lift and release it and, after releasing the article, be automatically locked in an open position ready to grip another article, said means comprising a latching member swingable between a latched and an unlatched position and being hook-shaped at one end, said latching member being operable in said latched position to lock one of said links to said support and to prevent relative movement between such link and the support, a catch member comprising a stub on said support adapted to engage the hook-shaped end of said latching member to hold said latching member in the latched position, and a pin-and-slot connection connecting said latching member to said one link for swinging movement of the latching member about the axis of the pin and for bodily movement of the latching member with the pin in a generally vertical direction, the pin of said pin-and-slot connection being mounted on said latching member near its other end, and the slot of said pin-and-slot connection being movable with said one link.

2. The grapple of claim 1 in which the latching member moves between the latched and the unlatched positions in response to raising and lowering of the grapple and is in the unlatched position as the grapple releases an article,

. and in which said pin is adapted to slide up and down in said slot as the latching member is moved in response to the raising and lowering of the grapple, and further including spring means located intermediate the ends of said slot and urging said latching member to swing about said pin toward the latching position when said pin is at one end of said slot and toward the unlatching position when said pin is at the other end of said slot, and a stop on said support for engaging the hook-shaped end of said latching member in its unlatched position as the grapple is releasing a gripped article whereby the pin is forced to the top of said slot so that said spring will urge the latching member toward the latching position.

3. In a grapple, the combination of, first and second members connected together for up and down movement relative to one another, a catch mounted on said first member, a latching element, a pin-and-slot connection between said latching element and said second member and mounting said latching element for swinging relative to said second member between latched and unlatched positions and also for bodily shifting relative to said second member between pre-lock and pre-release conditions, said latching element being operable in said latched position to engage said catch and restrict said second member to limited upward movement relative to said first member, said latching element being released from said catch in said unlatched position and leaving said second member free for upward movement relative to said first member, a spring acting on said latching element and biasing the latching element toward said latched position when the latching element is in said pre-lock condition, said spring biasing said latching element toward said unlatched position when the latching element is in said pre-release condition, means causing said latching element to shift bodily to said pre-lock condition when the second member is moved downwardly relative to the first member with the latching element disposed in its unlatched position, and means including said catch for causing the latching element to shift bodily to said prerelease condition when the second member is moved up wardly relative to the first member with the latching element in its latched position.

References Cited 3,155,416 11/1964 Buchik 294-410 HARVEY C. HORNSBY, Primary Examiner 

